The present invention relates to an apparatus for inspecting a thickness of wood board.
Wood materials for use as construction materials and the like are worked to predetermined dimensions by means of a specific cutting system. However, there may be a case where a worked material may contain a portion decreased in thickness because of the warpage of the material before subjected to the cutting process. In the case of a wood board 100 with warpage as seen from a longitudinal end thereof as shown in FIG. 7, for example, the board generally has a predetermined thickness t1 if its portions out of cutting lines (upper and lower cutting lines) shown in FIG. 8 are cut off. However, a thickness t2 of a central portion of the resultant board is smaller than the thickness t1. If the smaller thickness t2 is not within the range of allowance for the predetermined thickness t1, such a wood material is rejected because of deficient thickness. Similarly, the resultant board further contains thinner portions at transversely opposite ends thereof. In a case where such a wood material is used as material for laminated lumber, there occurs a gap between the materials. Therefore, a sufficient bond area between the materials cannot be attained. In addition, a sufficient pressure cannot be applied to portions to be pressed for bonding. This results in bonding failure between the materials.
In this connection, it has been the conventional practice to have an inspector visually inspect each cut wood material for determining the presence of a portion decreased in thickness. Unfortunately, since the visual inspection is a time-consuming job, the cutting system must be programmed to operate slower so that the cutting operation may proceed in tandem with the inspection process. Accordingly, the production efficiency is lowered. Furthermore, the inspection must be done by well-trained inspectors and hence, the inspection results vary depending upon the individuals. As a result, the manufactured wood materials are varied in quality.
In view of the foregoing, it is an object of the present invention to provide an apparatus for inspection of board thickness which accomplishes a speedy inspection and ensures stable product quality.
An apparatus for inspection of board thickness according to the present invention comprises: an apparatus for conveying a wood material worked for adjustment of board thickness thereof to a predetermined value; a board-thickness measuring apparatus for determining board thicknesses at plural points of the wood material as a measurement subject conveyed thereto based on outputs from displacement sensors located at plural different positions with respect to a widthwise direction of the wood material; a processing unit for determining the wood material to be a thickness deficient one if it is determined from the measurement results given by the board-thickness measuring apparatus that there is a predetermined amount of portion having a board thickness deviated from a range of allowance for the predetermined value along a conveyance direction; and a device for differentiating the wood material determined to be the thickness deficient one from the other wood materials (claim 1).
In the apparatus for inspection of board thickness arranged as mentioned above, the board-thickness measuring apparatus measures the thicknesses at plural points of the wood material as the measurement subject conveyed thereto. The processing unit determines the wood material to be a thickness deficient one if there is a predetermined amount of portion having the board thickness deviated from the range of allowance along the conveyance direction. The wood material determined to be the thickness deficient one is differentiated from the other wood materials. Thus is provided the apparatus for inspection of board thickness which ensures a speedy inspection and stable product quality without relying on the visual inspection.
In the above apparatus for inspection of board thickness (claim 1), the processing unit may determine the wood material to be a thickness deficient one based on at least one of the conditions that: the portion having the board thickness deviated from the range of allowance extends a predetermined length L1 or more along the conveyance direction, and not less than a predetermined number of the portions having the length of L1 and more are present per unit length of the wood material, and that: the portion having the board thickness deviated from the range of allowance extends a predetermined length L2( greater than L1) or more along the conveyance direction (claim 2). In this case, the determination as to whether the board thickness is deficient or not is made based on the two factors including the degree of the conveyance-wise length of the portion deviated in thickness from the range of allowance and the incidence of the thickness deficient portion. Hence, whether the board thickness is deficient or not can be determined correctly.
In the above apparatus for inspection of board thickness (claim 1), the displacement sensors may be disposed at a central position and positions near opposite ends with respect to the widthwise direction (claim 3). In this case, the board thicknesses are measured at three points including the central point. Therefore, the warpage or recess of the wood material can be assuredly detected.
In the above apparatus for inspection of board thickness (claim 1), an input device for entering a reference value for determination of the thickness deficient product may be connected to the processing unit (claim 4). In this case, the reference value for the determination of the thickness deficient product can be readily changed. Hence, a proper reference value can be programmed according to the grade or the like required of the wood material.
In the above apparatus for inspection of board thickness (claim 1), the differentiating device may be one that performs marking only on the wood material determined to be the thickness deficient one (claim 5). In this case, the marking provides for a definite and easy distinction of the thickness deficient product.